Hot dimpling machine and method



N v- 1955 K. A. CLARK, sR., ET AL 2,724,420

HOT DIMPLING MACHINE AND METHOD Filed Aug. 12, 1952 4 Sheets-Sheet l IN VEN TORS KENNETH A. CLARK SR. By VERNAL K. KENNEDY Azehf Nov. 22, 1955 K. A. CLARK, SR, ET AL 2,7

HOT DIMPLING MACHINE AND METHOD 4 Sheets-Sheet 2 Filed Aug. 12, 1952 INVENTORS KENNETH A. CLARK SR.

VERNAL K. KENNEDY Agent' v- 1955 K. A. CLARK, SR, ET AL 9 HOT DIMPLING MACHINE AND METHOD Filed Aug. 12, 1952 4 Sheets-Sheet 3 l 42 90 AW \N l5 INVENTORS KENNETH A. CLARK SR By VERNAL K KENNEDY Age n1 Nov, 22, 1955 K. A. CLARK, sR., ET AL 2,724,420

HOT DIMPLING MACHINE AND METHOD Filed Aug. 12, 1952 4 Sheets-Sheet 4 IN V EN TORS KENNETH A. CLARK SR.

BY VERNAL K. KENNEDY United States Patent r 2,724,420 nor DIMPLING MACHINE AND METHOD Kenneth A. Clark, Sr., Burbank, and Vernal K. Kennedy,

Van Nuys, Califi, assiguors to Lockheed Aircraft Corporation, Burbank, Calif.

Application August 12, 1952, Serial No. 304,034

8 Claims. c1. 153-41 This invention relates toa machine for a dimpling and riveting sheet metalparts and has particular reference to an improved hot dimpling arrangement operable alone or in combination with an automatic dimpling punching and riveting cycle such as disclosed in the application of Harness and Hruby, Serial No. 680,800 filed July 1, 1946, now Patent Number 2,620,876, granted December 9, 1952, entitled Automatic Riveting Machine.

Some high strength aluminum and/ or magnesium alloys available for use in aircraft construction show tendencies to crack during the dimpling operationrequired when flush rivets are to be used, and various methods of preheating the metal in the area to be dimpled have been tried in the past. One method is to heat the actual dimpling tools themselves, but this results in damage to the tools and inadequate heating of the area to be dimpled as the tools are complementary conical surfaces and,

therefore, the male punch initially touches the metal only at its tip while the female anvil makes a peripheral contact with the other surface of the work. If two or more sheets of metal are to be dimpled simultaneously it becomes increasingly ditlicult to effect adequate heating of the superimposed sheets of metal. Another hot dimpling method heretofore proposed is to apply annular heating members surrounding the actual dimpling tools, but this requires that the heat flow inwardly through the metal to be riveted to heat the actual area to be incorporated in the dimple, with the result that the metal in actual contact with the annular heating elements must be heated to above the temperature desired in the dimple area. Also, such prior hot dimpling methods have required that the rivet hole he pre-punched for use as a pilot for locating the dimpling tools with the result that the rivet hole forms a weak area at the apex of the dimple, the dimpling operations changing the sides of the rivet hole so that the riveting operation requires further upsetting of the rivet to fill the hole provided therefor.

It is accordingly an object of this invention to provide an improved machine for the hot dimpling of sheet metal wherein the sheet metal is heated in the actual area thereof to be dimpled, the dimple being formed in the sheet immediately after the heating thereof.

It is another object of this invention to provide an improved hot dimpling machine to preheat and dimple multiple layers of sheet material before punching a rivet hole in the center of the dimple, the heating of the area to be dimpled being done under pressure to assure intimate contact and heat flow through the multiple layers of material to be dimpled simultaneously.

It is a further object of this invention to provide an improved apparatus for hot dimpling sheet material prior to and as a part of a complete automatic riveting cycle involving dimpling, punching and riveting in sequence, as taught in the Harness, et al. patent referred to.

Other and further objects and advantages of this invention will become apparent as the detailed description proceeds in connection with the accompanying drawings of a preferred embodiment.

, 2,724,420 Patented Nov. 22, 1955 "ice In the drawings:

Figure 1 is a side elevation of a riveting machine showing the application of this invention to the apparatus of the Harness, et al. patent;

Figure 2 is a front view of the apparatus of Figure 1;

Figure 3 is an enlarged front view of the punch and anvil assembly during the preheating step of this invention;

Figure 4 is a view similar to Figure 3 showing the tooling after the heating element has been retracted and the dimpling and punching operations performed;

Figure 5 is a view similar to Figures 3 and 4 showing the tooling after the completion of the riveting operation;

Figure 6 is a side view of the heating element support and retracting mechanism;

Figure 7 is a section on the line 7-7 of Figure 6 showing the heatingelement retraction mechanism in side view; 0

Figure 8 is a plan view of the heating element support and retracting mechanism taken on the line 88 of Figure 6; and

Figure 9 is a schematic drawing of the apparatus operating the several steps of heating, dimpling, punching, and riveting, comprising the complete cycle of operation of the machine.

As shown on the drawings:

The hot dimpling step of this invention has been shown as incorporated in the automatic dimpling, punching and riveting machine as disclosed and described in detail in the Harness et al. patent previously referred to. For convenience the same reference numerals will be used as far as possible herein in describing analagous parts, to facilitate reference to the patent for details thereof which will not be repeated herein.

The machine includes a frame 10 of generally 6 shape having a base 11, alower jaw 12 and an upper jaw 13; the forwardly extending jaws and the body 10 being generally hollow and containing various working parts. An upwardly extending tubular boss 14 is provided on the lower jaw 12 adjacent its forward end to receive the lower anvil, die and punch to be subsequently described. The active work engaging elements of the machine arranged on the lower jaw 13 include a lower die and anvil carrier 15, guided for vertical movement in the tubular boss 14, and having its upper portion tapered or frusto-conical. A socket 16 is formed on the upper end of the carrier 15 to receive the shank of a die 17, the upper end of which has a die cavity or recess 19 complementary to the desired shape of the dimple to be formed in the workpiece. The die 17 is tubular, having a central vertical opening to slidably receive a rod-like punch 20 which is also used in a later stage of the cycle to upset the end of the rivet, as shown in Figure 5. A yoke-like member replaces the tubular stripper 21 of the patent and is slidable on the exterior of the die 17 and its upper face is adapted to engage the under side of the workpiece W. The carrier 15, the punch 20 and the member 90 are each individually operated by suitable power mechanisms, for example pneumatic cylinder and piston means. The means for operating the carrier 15 vertically comprises a cylinder 23, a piston 24 operable in the cylinder and toggle linkage 26 operated by the piston rod 25. This assembly is illustrated in Figure l. Actuating air pressure lines 27 extend from the opposite ends of the cylinder 23 to a fourway solenoid valve 28 in the jaw 12.

The means for operating the punch 20 includes a cylinder 29 attached to the carrier 15 and a piston 30 operating in the cylinder and having a rod 31extending from the lower end of the cylinder, as shown in Figures 1 and 9. A lever 32 is pivoted at the lower end of the cylinder 29 and has one end engaged by the piston rod 31 and its other end acting upwardly against a rod 33 guided in the carrier 15. Intermediate pushrods 35 and 36, illustrated in Figure 4, are arranged between the rod 33 and the punch 20 to slide in the carrier and die 17. A spring 37 is engaged under compression between the rod 35 and an enlargement of the rod 36 to yieldingly support the punch 20 for retraction. The weight of the workpiece W is sufficient to compress the spring 37 and press the punch 20 downwardly, and when the piston 30 is actuated'downwardly the rods 33 and 35 move upwardly to compress the spring 37 until the upper end of the rod 35 engages the end ofthe rod 36 so that force is positively transmitted to the punch 20 to form an opening in the workpiece. Flexible lines 40 and 40 deliver actuating air under pressure tothe opposite ends of the cylinder 29'and extend to a .solenoid operated valve 209 shown in-Figure 9.

The member 90 is separately urged upwardly to press against the underside of the workpiece W around the die 17. Vertical cylinder bores 41 are provided in the carrier 17 and rams 42 extend downwardly into the bores, as shown in Figure 4. The upper ends of the rams 42 are attached to the member 90 at 43. An air pressure valve 44 supplies actuating air under pressure to the bores 41 from a main supply line 45.

The upper jaw 13 of the machine carries a dimpling shoe 47 and a riveting shoe 48, best shown in Figures 1 and 9. The shoe 47 has an upwardly sloping arm 49 and its offset lower portion removably carries a male dimpling die 50. The riveting shoe 48 has a similar arm 51 and its lower portion has a vertical opening 52. The shoes 47 and 48 are mounted for individual vertical movement and simultaneous horizontal shifting.

The mechanism for shifting the shoes includes horizontal cylinders 63 and 64, and have pistons 65 provided with rods 66 which actuate the shoes. Air pressure lines supply air under pressure to the outer ends of the respective cylinders 63 and 64. The parts are related so that upon introducing air pressure to the cylinder 63 the riveting shoe 48 isbrought to the active position in line with the main ram 68 and upon supplying air pressure to the cylinder 64 the dimpling shoe 47 is moved to the position in alignment with the main ram. 'The shifting of one shoe to the active position simultaneously moves the other shoe to the inactive position.

The means for actuating the main ram 68 includes a vertical cylinder 69 mounted on the jaw 13 where its longitudinal axis is coaxial with the die 17. A piston 70 operates in the cylinder 69 and has a'rod 71 extending downwardly from the jaw 13. The lower end of the piston rod 71 carries a chuck '72 for the ram 68. The ram 68 is engagcable with the male dimpling die .50 to drive the same downwardly against the work W when the shoe 47 is in the active position and is adapted to move downwardly through the riveting shoe 48 when the latter is in its active position to drive the rivet. The-shank of the rivet is upset against the top of .the punch.20 and the female die 17 so that vertical movement of the punch 20 controls the dimensions of the driven rivet. A stop screw 73, shown in Figure l, is provided in the top of the cylinder 29 and is engageable by the piston 30 to limit downward travel of the punch 20. Adjustment of the screw 73 controls the position of the punch 20 for the riveting operation.

Referring again to the main cylinder .69, shOWn in Figure 9, a reduced stem 75 extends .upwardly'ffrom the piston 70 and slides through an opening in-the upper head of the cylinder. A washer 76 secured on-the upper end of the stem 75 and a spring 77 is arranged under compression between the cylinderhead and this washer to return the piston 70 and ram 68 to the raised position when air pressure is released from the cylinder. A cap 78 on the cylinder 69 houses the projecting stem '75, spring 77 anddisc 76. l

Rivet .feeding'. mechanism including a "chute-86 shown in Figures 3, 4 and 5., depositsrivetstin the rivet "5116648 4 when the latter is retracted, as described in the patent referred 10.

Prior to each riveting operation a rivet is supplied to the shoe 48. This rivet is retained in the shoe 48 while the latter is shifted into alignment with the main ram 68 and until it is forced into the opening in the workpiece W. The workpiece W is securely clamped between the dies 17 and 50 during the punching operation and the punch 20 is operated upwardly to form the opening in the dimpled material. Figure 4 shows the parts in the position after the punching operation where it will be seen that the die 50 has an opening for receiving the punch 20 as it moves upwardly. I

The arrangement so far described relates to the apparatus more fully disclosed by the patent referred to, to which the hot dimpling arrangement of the present invention has been added. It is to be noted that the complete combination is not essential to this invention as the subcombination of the heating and dimpling steps are usable alone if the punching and/or riveting operations are to be done elsewhere.

Heating of the immediate area in the work W which is subsequently to be dimpled by the above apparatus of the patent referred to, is accomplished by the lower yoke-like member '90 the arms of which contain electric heating elements 94, the member 90 being axially slidable onthe anvil 17 in the carrier 15 on the lower jaw 12 and by a retractable heating member 91 arranged to be swung beneath the dimpling shoe 47 with the shoe 47 pressed down thereon by the ram 68 to hold the workpieces W together by pressure e uivalent to that exerted during the dimplingl'step. The member 91 is supported by an offset connection 92 to an oscillating shaft 93. The offset connection 92 also carries embeddedelectric heating elements 94 for heating the member 91. These heating elements are wired through junction boxes 95 and 96 shown in Figure l. A thermocouple 112 mounted alongside the offset connection 92 serves to operate control means for maintaining a selected temperature in the heating elements 94.

The upper heating member 91 and its shaft 93 are carried by a plate like member 97 supported at its rear end by a hinge 98 fastened to the upper jaw 13. The plate 97 is yieldingly held up by bolts 99 and opposed springs 100 to provide operating clearance with the work while the heating member 91 is being oscillated into or out of its operative position, shown in Figure 3, where it is positioned between the work and the dimpling shoe 47. The positioning mechanism is best shown in Figures 6, 7 and 8 where a crank 101 on the shaft 93 is operated by linkage 102 connected to a piston 103 operating in a cylinder 104 having pneumatic connectionslGS and 106 controlled by a reversing valve 107. The crank 101 also operates a pair of electric switches tied into the machine control. One switch .108 is normally open and closed by the movement of the element 91 into the operative or heating position; and the other switch 1it9'is normally closed, and opened by the retraction of the heating element 91 into the inoperative position. The switch108 is used to establish a dwell period in the machine sequencing control circuit, and switch 189 restores the machine control for the next or dimpling step of the complete machine cycle.

Figures 2, 3 and 4 illustrate the sequence of operation in hot dimpling a workpiece W and Figure 5 shows the completion of the riveting operation, Figures 4 and 5 operating as taught in the patent referred to. The workpiece W isfirst positioned on the member 90 and then the upper heating member 91 swung down into position by operation of-the valve 197 to the position shown in Figure 9 which applies air pressure to the right handiend of the cylinder 1.04 through the line 106; The heating member 91 is heldslightly above the work surface by the hinged .platemember 97 to provide clearance during the swinging motion -50f the upper heating member 91, and this clearance is only partly taken up by liliting theanvil 17 and lower heating member 90 by operation of the air valve 23 to energize the piston 24 to the right as shown in Figure 9. The dimpling shoe 47 is swung to the right under the ram 63 by turning a valve 110 to energize the cylinder 64, and the ram is brought down to press the shoe 47 onto the heating element 91 and both down onto the workpiece by operating a valve 111 to apply pressure above the piston 70. Incidentally, the heating member 91 is provided with a dimple socket 112 to receive the dimple punch 54) so that pressure from the ram 68 is transmitted through the dimpling shoe to the heating member 91 as shown in Figure 3 for a selected dwell period determined by the character, thickness and number of layers of material to be simultaneously dimpled. After the heating period the ram is raised, whereupon the heating member 91 is swung out of the way, the heating member 90 low cred level. with the anvil 17 and the ram again lowered to perform the actual dimpling operation as in the prior patent. While the dimpling shoe is still held in the dimple just formed the punch 20 is forced upward to form the rivet improved hot dimpling apparatusthat is disclosed as fitting into an automatic dimpling and riveting cycle as taught in the Harness, et al. patent referred to, but that can be used alone in the event that the workpieces are to be predimpled for riveting elsewhere. Our improved hot dimpling apparatus preheats and dimples the work witlr out risk of cracking the dimpled area, and is readily adjustable to accommodate difierent rivet sizes and various combinations of the material to be riveted.

Having described only a form of our invention particularly suited for incorporation in the machine of the Harness, et al. patent, we do not desire to be limited to the specific details herein set forth, but wish to reserve to ourselves any variations or modifications that may appear to those skilled in the art and/ or fall within the scope of the following claims.

We claim as our invention:

1. In a dimpling machine including anvil means carrying a die, a ram, means for moving the ram towards the i die, a vertically movable shoe positioned between the ram and die in alignment therewith, and a dimpling die carried by the shoe, the combination of a first heating means can ried by said anvil and surrounding the die therein, said first heating means being arranged to contact the lower surface of the workpiece to be dimpled, a second heating means arranged to be interposed between said verticaliy movable shoe and the top of the workpiece to be dimpled to be pressed thereagainst by operation of the ram, and means to retract said second heating means following release of ram pressure whereby to clear the dimpling shoe for the dimpling operation.

2. A hot dimpling machine as in claim l wherein the second heating member is yieldingly supported clear of the workpiece when in operative position, said heating member being moved into contact with the workpiece by applying ram pressure thereto.

3. A hot dimpling machine as in claim 1 wherein means to retract the second heating means comprises a shaft on which said means is carried in offset relationship, and operating means to oscillate said shaft to swing said heating means into and out of alignment between the anvil and the dimpling die.

4. A hot dimpling machine as in claim 1 wherein the heating means comprise electric heating elements embedded in contact members cooperatively fitting the anvil and the dimpling die.

5. In combination with a dimpling machine including an axially movable anvil and an axially movable dimpling shoe, means for preheating the workpiece to be dimpled while in position between said anvil and shoe, comprising a first heating member carried by the anvil in contact with the lower side of the workpiece immediately surrounding the area to be dimpled, a second heating member arranged to be interposed between said dimpling shoe and the upper surface of the workpiece in the area thereof to be dimpled, means for operating said anvil and shoe to clamp said second heating element and workpiece together for heating the workpiece. and means for retracting said second heating member from between said shoe and workpiece for the dimpling operation.

6. The combination defined in claim 5 wherein the means for retracting the second heating member comprises a shaft carrying the member on an offset arm and means to oscillate said shaft to swing said member into and out of position between the shoe and workpiece.

7. The combination defined in claim 5 wherein the second heating member is carried by a hinged arm so arranged as to yieldingly hold the heating member in spaced relationship to the workpiece.

8. The method of preheating the local area of a workpiece in which a dimple is to be formed by a machine having an anvil at one side of the workpiece, a ram at the other side of the workpiece movable vertically toward and away from the anvil and a dimpling shoe shiftable and movable vertically at said other side of the workpiece, which method comprises applying a heat source to the first mentioned side of the workpiece in the area immediately surrounding the anvil, introducing a second source of heat between said shoe and said other side of the workpiece, operating the ram against said shoe to cause the shoe to press the second source of heat against said other side of the workpiece, retracting the ram, and then shifting the said second source of heat out of alignment with the ram.

References Cited in the file of this patent UNITED STATES PATENTS Creighton Dec. 20, 1949 

